Harnessing lignin/polyvinyl alcohol-polyethylene glycol copolymer synergy for improved mechanical and barrier properties in sustainable packaging applications

The transformation of lignin into a valuable biomaterial offers an innovative approach to sustainable packaging and a circular bioeconomy. In this study, we have developed sustainable films based on a polyvinyl alcohol-polyethylene glycol copolymer with internal plasticizing properties, reinforced with renewable dealkaline lignin as the active ingredient, thereby eliminating the need for external plasticizers. The films were developed using a solvent casting technique and were analyzed for their mechanical strength, flexibility, barrier properties, and functional performance. The integration of lignin (at 10 wt%) with the polymer synergistically enhanced the tensile strength to 10.35 ± 0.2 MPa, the water contact angle to 71.2 ± 4.8°, and the UV-blocking ability to 84% across the UV range. Additionally, the films demonstrated reduced water vapor and oxygen permeability, thereby enhancing overall barrier performance. The characterization techniques like FTIR and XRD indicated strong intermolecular interactions and amorphization in the composite films, while TGA confirmed better thermal stability than blank films. Beyond their physical attributes, the films exhibited improved antioxidant activity and significant antibacterial activity against common foodborne pathogens (Escherichia coli and Staphylococcus aureus). Further, the finalized film batch effectively inhibited visual browning and prolonged the shelf life of fresh-cut bananas, as demonstrated by 5-day preservation studies. Soil burial tests confirmed the physical disintegration of the films within 12 days, highlighting the potential of lignin as a high-value additive in a PVA-PEG copolymer matrix for a sustainable, eco-friendly food packaging solution.